Attention-deficit/hyperactivity disorder (ADHD) is a common disorder among adolescents but can be a challenge to diagnose in this population for several reasons. Obvious symptoms of hyperactivity and impulsivity are displayed less frequently than in younger children. Direct observation by potential raters is more limited because adolescents spend less time with parents and usually have multiple teachers throughout the day. Also, adolescents often suffer from psychiatric comorbidities, which affect the presentation of ADHD and can confound the diagnosis. Similarly, impaired social skills and academic performance may result from this disorder or for other reasons. These difficulties underscore the importance of a careful and comprehensive assessment that includes parent-, teacher-, and self-reported measures of functioning in several environments, including school, home, and work. Because ADHD is chronic and usually impairing in several domains (eg, social skills, academic performance, family relations, emotional health, driving), adequate treatment is essential. However, there are relatively few treatment studies in adolescents. Stimulant agents are well established as first-line medication treatment for both school-aged children and adults. Existing data support that this is also the case with adolescents. Specifically, both an extended-release formulation of methylphenidate, osmotic-release oral system (OROS MPH; CONCERTA) and a mixed amphetamine salts extended-release (MAS XR; Adderall XR) have demonstrated efficacy and safety in reducing the core symptoms of ADHD in well-designed, multisite, placebo-controlled, double-blind trials. Additional research is needed to further refine diagnostic and assessment tools in the adolescent population.